Skin metabolism

Administration of protein substrates (amino acids) may result in nausea, fever, flushing of the skin, metabolic acidosis or alkalosis, and decreased phosphorus and calcium blood levels. 

PN can cause mechanical or technical (e.g., malfunctions in delivery system and catheter-related complications), infectious (e.g., colonization of the catheter or direct microbial invasion of the skin), metabolic (Table 60-3), and nutritional complications. 

Bando H, Mohri S, Yamashita F, Takakura Y, Hashida M (1997) Effects of skin metabolism on percutaneous penetration of lipophilic drugs. J Pharm Sci 86 759-761. 

J. Boehnlein, A. Sakr, J. L. Lichtin, R. L. Bronaugh, Characterization of Esterase and Alcohol Dehydrogenase Activity in Skin. Metabolism of Retinyl Palmitate to Retinol (Vitamin A) During Percutaneous Absorption , Pharm. Res. 1994, 11, 1155-1159. 

Transdermai system In contrast to oral estradiol, the skin metabolizes estradiol via the transdermai system only to a small extent. Therefore, transdermai use produces therapeutic serum levels of estradiol with lower circulating levels of estrone and estrone conjugates, and requires smaller total doses. 

Pharmacokinetics Poorly absorbed by topical administration. Well absorbed from mucous membranes and traumatized skin. Metabolized in liver and by hydrolysis with cholinesterase. Minimal excretion in urine. 

Mechanism of Action A synthetic vitamin Dj analog that regulates skin cell (kerat-inocyte) production and development. Therapeutic Effect Preventing abnormal growth and production of psoriasis (abnormal kerafinocyte growth). Pharmacokinetics Minimal absorption through intact skin. Metabolized in liver. 

Pharmacokinetics Maybe absorbed from intact skin. Metabolized in liver. Excretedin the urine. 

Pharmacokinetics Absorption is variable and dependent upon many factors including integrity of skin, dose, vehicle used, and use of occlusive dressings. Small amounts maybe absorbed from the skin. Metabolized in liver. Excreted in the urine and feces. 

In Figure 5, typical chromatograms of plasma components of DIL are shown for transdermal and oral deliver. The peaks 1, 2, and 3 are, respectively, verapamil as the internal standard, DIL and deAcDIL. The peaks 4 and 5 are unidentified metabolites (12, 13). Both the extent and number of different metabolites are less in topical delivery. Skin metabolism and absorption of ionized species is virtually unknown and remains an intriguing area for study. 

Thus the balance between external and internal loading appears to play an important role in skin metabolism and healing. Tension applied to the epidermis appears to lead to cell division (hyperplasia) whereas compression of the dermis leads to scar tissue resorption. These observations appear to fit the general model that external tension promotes tissue augmentation and external compression leads to tissue destruction (catabolism). 

FACTORS INFLUENCING DERMAL ABSORPTION 319 Factors Related to the Skin 319 Intraspecies Differences 319 Inter-individual Differences 319 Skin Condition 319 Anatomical Site 320 Skin Metabolism 320... 

It is commonly known that the skin contains a large range of enzymes capable of metabolizing topically applied compounds. Eor pesticides, esterase activity is among the most important (van de Sandt et al, 1993 Hewitt et al, 2000). Although the stratum comeum is generally accepted as the most important barrier in skin absorption, there are some indications that skin metabolism in other skin layers influences the percutaneous absorption of compounds (Potts etal, 1989). The interrelation between metabolism and absorption rate, however, has not been unequivocally established. 

PNLM 1. Administration, Cutaneous. 2. Skin—metabolism. 3. Skin— anatomy histology. W1 DR893B v.83 1997 / WB 340 M486 1997]... 

Lopez, R.F. Collett, J.H. Bentley, M.V. Influence of cyclodextrin complexation on the in vitro permeation and skin metabolism of dexamethasone. Int. J. Pharm. 2000,... 

If they are ingested, dyes and particularly those that have an azo group can be metabolized by the intestinal microflora or by the liver enzymes. So, their effects can occur in organs responsible for metabolism or elimination, like the liver and urinary tract. Skin metabolism may also be responsible for the transformation of dyes, for example, those from colored textiles that can leach from the fabric and migrate to the skin. For example Disperse Orange 3 is degraded to p-phenylenediamine (PPD) and nitro-aniline in the skin (Figure 1). Direct Blue 14 (Cl 23850), after azo reduction, converts to the aromatic amine o-toluidine and other amines when incubated with cultures of Staphylococcus aureus. 

Roche). Effects on skin metabolism W. P. Raab, B. M, Gmeiner, Arch. Dermatol Res. 256, 247 (J976). Toxicity study in organ culture D- R. Bard. I. Lasnitzki, Brit. J. 

In vitro diffusion cell studies are frequently conducted to evaluate the skin absorption of chemical compounds. It may be the only ethical way of obtaining himran skin absorption data for a potentially toxic compound. The in vitro system also permits the evaluation of skin metabolism if the viability of skin is maintained. Because the skin is isolated in the diffusion cell, there is no metabolic interference from enzymes in other parts of the body. A number of important decisions have to be made when conducting an in vitro absorption smdy, and this has led to some controversy regarding how a good study should be performed. 

Boehnlein, J., Sakr, S., Lichtin, J.L., and Bronaugh, R.L., 1994, Characterization of esterase and alcohol dehydrogenase activity in skin. Metabolism of retinyl palmitate to retinol (vitamin A) in skin during percutaneous absorption, Pharm. Res., 11 1155-1159. 

Amin, S. Huie, K. Balanikas, G. Hecht, S.S. Pataki, J. Harvey, R.G. High stereoselectivity in mouse skin metabolic activation of methylchrysenes to tumorigenic dihydrodiols. Cancer Res. 1987, 47, 3613-3617. 

In our studies to date, the compounds in which oral and dermal studies were done have shown qualitative similarities in urine metabolic patterns. This was noted in the methyl ethyl aniline, CGA-73102, methidathion and atrazine studies discussed in this paper. Thus, based upon our experience, there is no reason to believe that major metabolic differences occur due to oral vs. dermal treatment routes. As noted by Pannatier et al ( ), specific examples of skin metabolism are scarce, except for steroid hormones. 

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